NXP Semiconductors LPC43 Series User Manual

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NXP Semiconductors LPC43 Series User Manual Manual pdf 559 page image

UM10503 All information provided in this document is subject to legal disclaimers. © NXP B.V. 2012. All rights reserved.User manual Rev. 1.3 — 6 July 2012 559 of 1269NXP Semiconductors UM10503Chapter 23: LPC43xx USB0 Host/Device/OTG controllerTable 438. dTD tokenAccess Bit Name Description- 31 - reservedR/W 30:16 Total_bytes Total bytesThis field specifies the total number of bytes to be moved withthis transfer descriptor. This field is decremented by thenumber of bytes actually moved during the transaction and itis decremented only when the transaction has beencompleted successfully.The maximum value software can write into this field is0x5000 (5 x 4 kB) for the maximum number of bytes five pagepointers can access. Although it is possible to create atransfer up to 20 kB this assumes that the first offset into thefirst page is zero. When the offset cannot be predetermined,crossing past the fifth page can be guaranteed by limiting thetotal bytes to 16 kB. Therefore, the maximum recommendedTotal-Bytes = 16 kB (0x4000).If Total_bytes = 0 when the host controller fetches thistransfer descriptor and the active bit is set in the Status fieldof this dTD, the device controller executes a zero-lengthtransaction and retires the dTD.Remark: For IN transfers, it is not a requirement thatTotal_bytes is an even multiple of Max_packet_length. Ifsoftware builds such a dTD, the last transaction will always beless than Max_packet_length.RO 15 IOC Interrupt on completeThis bit is used to indicate if USBINT will be set when thedevice controller is finished with this dTD.1 - USBINT set.0 - USBINT not set.- 14:12 - reserved